Microcirculation of secondary bone tumors in vivo: The impact of minor surgery at a distal site

Microcirculatory properties of tumors play a pivotal role in tumor progression and inefficacy of therapies. It has been hypothesized that surgical interventions result in an accelerated tumor growth by increasing the level of pro‐angiogenic cytokines with subsequent amplification of tumor angiogenesis. To characterize the microvascular properties of secondary bone tumors in vivo and determine the impact of minor surgery on the microcirculation, we performed intravital microscopy over 25 days using a xenograft model of breast cancer tumor growth (MCF‐7) in bone. After engraftment of tumors the mice were treated with a mastectomy versus no surgery. Tumor growth was accompanied by angiogenic sprouting and decreased vascular diameters while blood flow rate and tumor perfusion remained constant. Mastectomy initially led to a significant reduction of functional vascular density, increased vascular diameter, and decreased blood flow velocities. However, neither tumor growth nor tissue perfusion was different between the groups. The presented study corroborates the assumption that tumor microcirculation in bone exhibits similar time‐dependent alterations compared to soft tissue tumors. A minor surgical intervention did not change tumor growth kinetics however microcirculatory properties were altered. Whether major surgery has an impact on tumor growth in bone should be clarified in further studies. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 28:1515–1521, 2010     

Bone mineralization defects and vitamin D deficiency: Histomorphometric analysis of iliac crest bone biopsies and circulating 25‐hydroxyvitamin D in 675 patients

Parathyroid hormone (PTH) is only one measurable index of skeletal health, and we reasoned that a histomorphometric analysis of iliac crest biopsies would be another and even more direct approach to assess bone health and address the required minimum 25‐Hydroxyvitamin D [25(OH)D] level. A cohort from the northern European population with its known high prevalence of vitamin D deficiency therefore would be ideal to answer the latter question. We examined 675 iliac crest biopsies from male and female individuals, excluding all patients who showed any signs of secondary bone diseases at autopsy. Structural histomorphometric parameters, including osteoid indices, were quantified using the Osteomeasure System according to ASBMR standards, and serum 25(OH)D levels were measured for all patients. Statistical analysis was performed by Student's t test. The histologic results demonstrate an unexpected high prevalence of mineralization defects, that is, a pathologic increase in osteoid. Indeed, 36.15% of the analyzed patients presented with an osteoid surface per bone surface (OS/BS) of more than 20%. Based on the most conservative threshold that defines osteomalacia at the histomorphometric level with a pathologic increase in osteoid volume per bone volume (OV/BV) greater than 2% manifest mineralization defects were present in 25.63% of the patients. The latter were found independent of bone volume per trabecular volume (BV/TV) throughout all ages and affected both sexes equally. While we could not establish a minimum 25(OH)D level that was inevitably associated with mineralization defects, we did not find pathologic accumulation of osteoid in any patient with circulating 25(OH)D above 75 nmol/L. Our data demonstrate that pathologic mineralization defects of bone occur in patients with a serum 25(OH)D below 75 nmol/L and strongly argue that in conjunction with a sufficient calcium intake, the dose of vitamin D supplementation should ensure that circulating levels of 25(OH)D reach this minimum threshold (75 nmol/L or 30 ng/mL) to maintain skeletal health. © 2010 American Society for Bone and Mineral Research     

Correlations Between Iron Status Markers During Normal Pregnancy in Women with and without Iron Supplementation

The aim was to evaluate relationships between iron status markers (haemoglobin, erythrocyte indices, serum iron, serum transferrin, serum transferrin saturation, serum ferritin) in normal pregnancy. Iron status markers were measured at 4-week-intervals during pregnancy and postpartum in 120 healthy women; 62 had daily treatment with tablets containing 66 mg ferrous iron, 58 were treated with placebo. Placebo-treated: Ferritin displayed positive correlations with transferrin saturation during 2nd and 3rd trimester. There were positive correlations between ferritin, erythrocyte MCV and MCH during 2nd and 3rd trimester and postpartum. Prior to delivery and postpartum, ferritin demonstrated positive correlations with haemoglobin. Transferrin saturation showed positive correlations with MCV, MCH and MCHC during 2nd and 3rd trimester and postpartum. Transferrin saturation displayed positive correlations with haemoglobin prior to delivery and postpartum. Iron-treated: In general, there were no correlations between iron status markers. Positive correlations appeared postpartum between ferritin, transferrin saturation and MCHC but not with haemoglobin. Transferrin saturation showed a positive correlation with MCH postpartum, but not with haemoglobin. Conclusion: The patterns of relationships in placebo-treated women were consistent with iron deficient erythropoiesis.     

DexaBEAM versus ICE salvage regimen prior to autologous transplantation for relapsed or refractory aggressive peripheral T cell lymphoma: a retrospective evaluation of parallel patient cohorts of one center

High-dose chemotherapy (HDT) followed by autologous stem cell transplantation (ASCT) is considered standard in the treatment of patients with relapsed or refractory aggressive peripheral T cell lymphoma (PTCL). However, the optimal salvage regimen before ASCT has not yet been established. We retrospectively analyzed 31 patients with relapsed or refractory aggressive PTCL after anthracycline-based first-line chemotherapy who received either DexaBEAM (dexamethasone, carmustine, etoposide, cytarabine, and melphalan; n?=?16) or ICE (ifosfamide, carboplatin, and etoposide; n?=?15) regimen as first salvage chemotherapy followed by HDT/ASCT. The overall response rate (OR) was significantly higher for patients treated with DexaBEAM (69 %; 95 % confidence interval 46.0–91.5 %) as compared to the ICE group (20 %; 95 % confidence interval ?0.2–40.2 %; P?=?0.01), with higher complete response (CR; 38 %; 95 % confidence interval 13.8–61.2 %; vs. 7 %; 95 % confidence interval ?6.0–19.6 %) as well as partial response (PR; 31 vs. 13 %) rate. Changing regimen due to failure of first salvage therapy, 12 patients initially receiving ICE still achieved an OR of 58 % (33 % CR, 25 % PR) with DexaBEAM as second salvage therapy, whereas in three patients receiving ICE after DexaBEAM failure, only one achieved an OR (1 PR). Median progression-free survival was significantly higher in the DexaBEAM group (6.4 vs. 2 months; P?=?0.01). Major adverse event in both groups was myelosuppression with higher but tolerable treatment-related toxicity for patients in the DexaBEAM group. For all patients proceeding to HDT/ASCT, a 3-year overall survival was 50 %. Together, considering the limitations of the retrospective design of the evaluation and the small sample size, our data suggest that DexaBEAM salvage chemotherapy is superior to ICE for patients with relapsed or refractory aggressive PTCL for remission induction prior to autologous transplantation, with higher but manageable treatment-related toxicity.     

Diabetes mellitus secondary to pancreatic diseases (Type 3c) — Are we neglecting an important disease?

Type 3c diabetes mellitus (T3cDM) is a clinically relevant condition with a prevalence of 5–10% among all diabetic subjects in Western populations. Its prevalence and clinical importance have been underestimated and underappreciated so far. In contrast to the management of type 1 or type 2 diabetes, the endocrinopathy in T3cDM is very complex and complicated by additional present comorbidities such as maldigestion and concommitant qualitative malnutrition. The failure to correctly diagnose T3cDM leads to failure to implement an appropriate medical therapy of these patients. Physicians should screen for important and easily reversable pathological conditions such as exocrine insufficiency, lack of fat-soluble vitamins (especially vitamin D) and impairment of fat hydrolysis and incretin secretion which are found very commonly in T3cDM. Since most patients with T3cDM suffer from chronic pancreatitis, physicians must additionally be aware of the elevated risk of pancreatic cancer in this subset of patients.     

Collybistin activation by GTP-TC10 enhances postsynaptic gephyrin clustering and hippocampal GABAergic neurotransmission

In many brain regions, gephyrin and GABA_A receptor clustering at developing inhibitory synapses depends on the guanine nucleotide exchange factor collybistin (Cb). The vast majority of Cb splice variants contain an autoinhibitory src homology 3 domain, and several synaptic proteins are known to bind to this SH3 domain and to thereby activate gephyrin clustering. However, many functional GABAergic synapses form independently of the known Cb-activating proteins, indicating that additional Cb activators must exist. Here we show that the small Rho-like GTPase TC10 stimulates Cb-dependent gephyrin clustering by binding in its active, GTP-bound state to the pleckstrin homology domain of Cb. Overexpression of a constitutively active TC10 variant in neurons causes an increase in the density of synaptic gephyrin clusters and mean miniature inhibitory postsynaptic current amplitudes, whereas a dominant negative TC10 variant has opposite effects. The enhancement of Cb-induced gephyrin clustering by GTP-TC10 does not depend on the guanine nucleotide exchange activity of Cb but involves an interaction that resembles reported interactions of other small GTPases with their effectors. Our data indicate that GTP-TC10 activates the major src homology 3 domain-containing Cb variants by relieving autoinhibition and thus define an alternative GTPase-driven signaling pathway in the genesis of inhibitory synapses.Chemical synaptic transmission between neurons requires the tight packing of ionotropic neurotransmitter receptors in the postsynaptic plasma membrane. Core components of many inhibitory GABAergic postsynapses are the cell adhesion protein neuroligin 2 (NL2), the scaffolding protein gephyrin, the guanine nucleotide exchange factor (GEF) collybistin (Cb), and GABA_A receptors (GABA_ARs) (1, 2). The assembly of such GABAergic postsynapses is triggered by the interaction of NL2 with the src homology 3 (SH3) domain of Cb. This leads to the activation of Cb, which is otherwise autoinhibited by intramolecular interactions of its SH3 domain with the Dbl homology (DH) and pleckstrin homology (PH) domains, followed by membrane recruitment of Cb and synaptic accumulation of gephyrin and GABA_ARs (3). However, this NL2/Cb/gephyrin/GABA_AR interaction cascade cannot account for the formation of all GABAergic synapses, because in the hippocampus of NL2 KO mice gephyrin and GABA_AR clusters are lost only from perisomatic regions of CA1 pyramidal neurons (3). In contrast, deletion of Cb leads to a loss of gephyrin from both perisomatic and dendritic postsynapses (4). Thus, the formation of a substantial subset of GABAergic postsynapses must be regulated by Cb-interacting proteins other than NL2.Another class of Cb interaction partners with a potential role in gephyrin clustering are small Rho-like GTPases. They regulate many fundamental cellular processes, including actin cytoskeleton rearrangements (5), and the actin cytoskeleton plays an important role in the formation of inhibitory postsynapses, particularly at early stages of synapse formation (6, 7). The small GTPase Cdc42 is an established Cb substrate (8–10), and a recent analysis of 12 Rho-like GTPases identified Cdc42 as the only family member that can be activated in vitro by the human Cb ortholog hPem2 (11). However, Cdc42 expression is not required for gephyrin and GABA_AR clustering at postsynapses, indicating that Cb may regulate cytoskeleton remodeling by activating other Rho-like GTPases (10). The small GTPase most closely related to Cdc42 is TC10. Its sequence [67.4% amino acid identity (12)] and structure (13) are similar to those of Cdc42, it shares common cellular functions and effectors with Cdc42 (14), and profilin, an actin and gephyrin binding protein (15, 16), is an effector of TC10 (14). In contrast to Cdc42, which is ubiquitously expressed in the mammalian brain, the expression of TC10 is limited to specific areas, including the CA1 region of the hippocampus (17), where the most prominent reduction in gephyrin and GABA_AR clustering is observed in Cb KO mice (4). Here we provide evidence for an effector-type binding of GTP-TC10 to the PH domain of Cb that results in Cb activation, triggers synaptic gephyrin clustering, and enhances GABAergic neurotransmission.